And as it turned out, some bosses achieved much better results
than others. Mathematically, taking a boss in the 10th
percentile of productivity and replacing them with a supervisor
in the 90th percentile was the rough equivalent of adding an
extra worker to a nine-person team.

"If bosses were mere decorations, one would expect no variation"
between them, the researchers write. "The fact there is
wide variation...implies that there is a substantial productivity
effect that bosses confer on their teams."

So what were the good bosses doing right? The researchers
considered two possibilities. Either a boss might have been
really good at motivating their team (i.e., they were a
cheerleader, or maybe a drill sergeant) or they might have taught
employees lasting skills (i.e., they were a coach). By
looking at how well workers sustained their productivity after
switching supervisors, the team concluded that teaching
accounted for about two-thirds of a boss's impact on his
workers' productivity.